I find it difficult to understand why some reviewers have found it so dificult to fit this item. Please believe me that I am not trying to appear "smart". Yes, it could be better designed but it took me less than two minutes to fit and required no special tools. The connector is perfectly adequate and the pins wont bend if the connector is aligned properly before it is pushed into place. The operation just needs a bit of patience and some thought about what you are doing.
The following technique worked for me: Place the radio face down on the lap or a firm surface with the battery compartment open. Hold the battery pack horizontally just above the battery compartment using one hand. With the other hand, bend the connecting cable vertically downwards and bend the connector end of the cable back to the horizontal again (away from the battery) so that the cable forms a "Z" shape. The cable will stay in this shape and it is easy to hold the battery in one hand and align the plug correctly against the pins on the connector in the radio. Unless you have large fingers (in which case use a small flat screw driver blade or similar) push the plug firmly into place on the connector using a finger tip from your free hand. This does not require undue force. Finally, twist the cable into place so that it forms a neat loop between the end of the battery and the radio. I had no difficulty getting the lid of the battery compartment to slide back in place.
So why only 4 stars? Because the battery pack should be included as part of the radio, not an additional item. Overall, the battery pack has made using the radio far more flexible for me and I would recommend it. The signal level is not very good in some parts of our house and the battery pack makes it really easy to move the radio about to find a suitable location with a reasonable signal level.
I have been using it for about 2 weeks now and it seems to be maintaining charge well.